The first part of this verse seems to be a quotation from Septuagint Psalm 4.4. The New Testament text is exactly like that of the Septuagint, “be angry and do not sin,” but the first verb in the Hebrew text of Psalm 4.4 seems to indicate fear, and in the context the notion of anger seems out of place. So Good News Translation “Tremble with fear and stop sinning.” But Revised Standard Version, New English Bible, Zürcher all translate the first verb by “Be angry.” In a formal sense it is a command, “Be angry” (so Revised Standard Version), but this imperative functions as a concession, that is, “Be angry, if you must” or “You are bound to get angry, but….” The main point the writer makes is that anger should not be nourished: “do not let the sun go down on your anger” (Revised Standard Version). Sunset marked the end of one day and the beginning of another day; a Christian should not continue to be angry with his fellow believer from one day to the next but should seek reconciliation at once. The Greek noun for “anger” occurs only here in the New Testament. Accordingly, some (Westcott, Murray) want to understand the noun here to mean “provocation”; if this is taken in the passive sense, it denotes the result of being provoked and so means “irritation, anger” (so Robinson); but if it is taken in the active sense, then it means a cause of irritation to others.

In some languages it is necessary to indicate the reasons for being angry, and therefore the conditional clause If you become angry must sometimes be expanded as “If you become angry with someone” or “It may happen that you get angry, but….” The second part of this condition, namely, do not let your anger lead you into sin, may be translated as a causative, for example, “do not let that cause you to sin” or “do not permit how you feel to cause you to do wrong.”

Rather than the statement do not stay angry all day, it may be important to indicate the need for ceasing to be angry, for example, “be sure to cease being angry by evening” or “… before the sun has gone down” or “before the end of the day.”

Quoted with permission from Bratcher, Robert C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Ephesians. (UBS Handbook Series). New York: UBS, 1982. For this and other handbooks for translators see here .